Unable to mirror towards landscape mode on my new TV using my new ProMax, prior to recording or taking a picture.

During mirroring, my television screen stays on portrait mode even after I turn my ProMax to landscape mode. Worse yet, my picture or video will look 90 degrees sideways during preview, while I hold my phone on landscape angle.

Only after I take a picture or video will I then be able to see it on landscape mode. I have also made sure the PORTRAIT ICON is OFF, yet problem persists. Please help as even apple care specialist have been unable to resolve. I returned my iPhone X for this very same reason. Ironically, my iPhone 7 Plus, which has the latest updates, works just fine in landscape mirroring mode.